Involvement of nitric oxide donor compounds in the bactericidal activity of human neutrophils in vitro

The bactericidal activity of human neutrophils against extracellular and facultatively intracellular bacteria was studied in the presence of the nitric oxide (NO) donors sodium nitroprusside (SNP) and 3-morpholinosydnonimine (SIN-1), a molsidomine metabolite. SNP and molsidomine are drugs commonly used as nitrovasodilators in coronary heart disease. It is demonstrated here that the NO donor compounds themselves did not affect the viability and survival of the bacterial strains tested. Neither SNP nor SIN-1 had any effect on the process of bacteria ingestion. In contrast, NO donors enhanced the ability of neutrophils to kill Escherichia coli, Proteus vulgaris and Salmonella Anatum. However, strains differed in their susceptibility to SNP- and SIN-1-mediated killing by neutrophils. Removal of the superoxide anion reduced the bactericidal activity of SNP- and SIN-1-treated neutrophils against E. coli and S. Anatum. This suggests that the NO derivatives formed in the reaction of NO generated from donors with the reactive oxygen species released by phagocytosed neutrophils potentiate the bactericidal activity of human neutrophils in vitro. The above original observation discussed here suggests clinical significance for the treatment of patients with nitrovasodilators in the course of coronary heart disease therapy.